Patients with newly diagnosed gestational diabetes will be recruited. The control group with get routine diet and exercise counseling. The intervention group will be instructed to get moderate-to-vigorous intensity exercise; they will walk on a treadmill one time with supervision in order to be instructed how hard to work. All participants will keep an exercise log for 3 weeks and will wear an accelerometer for 1 week. The primary outcome is glucose control, specifically the need for medication in treatment of their diabetes. The hypothesis is that moderate or greater intensity exercise will better control glucose and lead to less need for medication management.